Generally speaking, the present invention relates to audible alarm devices and more specifically, audible alarm devices that utilize piezoelectric transducers of the type that convert electrical energy into sound energy wherein an acoustical loading means in spaced relation to a piezoelectric transducer and a voltage doubling means electrically coupled to circuitry including a power supply means, a pulsator means responsive to the power supply means and an alarm means electrically coupled to the pulsator means produce an efficient high output audible alarm.
Audible alarm devices utilizing piezoelectric transducer are in common use in many different applications requiring an audible warning signal including fault alarms, fire and smoke detection signals, and monitors for medical instruments. In many other applications including some intrusion alarms and in general applications requiring high outputs, piezoelectric alarm devices have not previously been used because they do not generally produce a sufficiently high volume of sound output for the application. Also, minimum standards are now being set for sound output of alarms utilized in such applications as fire and smoke detectors; accordingly, if piezoelectric transducers are to continue to be used in such applications, an increase in sound volume will be necessary. Previous work toward the objective of producing a volume level of sound higher than can be achieved in alarm devices utilizing piezoelectric transducers of the same size can be found in Sweany et al, U.S. Pat. No. 3,890,612 dated June 17, 1975. An embodiment of the present invention improves upon the Sweany patent by utilizing a voltage doubling means and an aperture terminated resonant cavity in combination with a piezoelectric transducer having three electrodes (previously disclosed in Sweany, U.S. Pat. No. 3,815,129 dated June 4, 1974) and an integrated circuit packaged (previously disclosed in Birt et al. U.S. Pat. No. 3,922,672 dated Nov. 25, 1975). As a result of the use of integrated circuitry and a voltage doubling means the weight and size of the present invention are significantly less than the device disclosed in Sweany et al., U.S. Pat. No. 3,980,612. This design feature and others increase the applicability of the present invention over devices of similar function.
Accordingly, a feature of the present invention is to provide an improved high output audible alarm device that utilizes a piezoelectric transducer of the type that converts electrical energy into sound energy. Another feature of the present invention is to provide a high output audible alarm device with reduced weight and size to that of conventional audible alarm devices. Another feature of the present invention is to provide an audible alarm system yielding a highly efficient alarm which is compatible with logic circuitry. Another feature of the present invention is to provide a high output audible alarm device for applications where low voltage power supplies are desired or mandatory. Yet another feature of the present invention is to provide an audible alarm device that includes a piezoelectric transducer, an amplifier means, a pulsator means and a power supply means cooperating with a voltage doubling means to produce a pulsating high output audible alarm. Yet another feature of the present invention is to provide a high output audible alarm device including a piezoelectric transducer in spaced relation to an acoustical loading means in combination with an amplifier means, a pulsator means, and a power supply means. Still another feature of the present invention is to provide a high output audible alarm device including a piezoelectric transducer in spaced relation to an acoustical loading means in combination with a voltage doubling means, an amplifier means, a pulsator means, and a power supply means. These and other features of the invention will become more apparent from the following description taken in conjunction with the accompanying drawings which follow: